The present invention applies to air data (that is being relative to the air) intended for the control of the aircraft or the engines thereof, including the following data or parameters:                primary parameters, being directly measured on the aircraft using usual means: Ps (static pressure), Pt (total pressure) and TAT (total temperature); as well as        derived parameters, being usually calculated using primary parameters: Mn (Mach number), CAS (calculated air speed), Alt (altitude pressure).        
Such air data are important for the control of the aircraft as well as for the control of the engines, the use of erroneous values by embedded systems being able to result in a control loss for the aircraft or the engines. For instance, too low an air speed, being not detected by a control system of the aircraft, could result in the latter engine stalling if it is used. As far as the control of an engine is concerned, using an erroneous temperature value could generate a thrust and/or pumping loss (switching off the engine could then be possible).
Numerous incidents were, in the past, either directly or indirectly, the result of using erroneous air data.
Thus, the current control systems of the aircraft and the engines in general comprise systems for selecting air data allowing to remove an erroneous data. Such systems are generally based on the processing of the results of a plurality of redundant measurement sources. Thus, if one of them supplies an erroneous data, being detected thanks to a comparison with the (correct) data from the other sources, such corresponding air data and source are invalidated, that is are no longer used in the remainder of the flight.
However, with this usual solution, a problem could occur when several sources are affected by a same cause (such as, for instance, frost).
Furthermore, current control systems of the aircraft and the engine also comprise frost detection specific logics based on abnormal speed or temperature variations. However, it is not sure that a frost case is not able to induce speed or temperature variations outside the thresholds provided by models. Furthermore, defect cases other than frost (error of the calculator transmitting the air data, corruption of the communication means between the systems, mechanical or electrical defect of the measurement probe), could also, theoretically, affect the validity of an air data.
The present invention aims at overcoming such drawbacks. It relates to a method allowing detection, in a particularly reliable and efficient way, of any erroneous air data on an aircraft during a flight of the latter, such a method allowing, more specifically, all the above mentioned cases to be included.